The purpose of this project is to continue development of theoretical models of dose-response relationships for ionizing radiation at the cellular level and to begin the development of generalized conceptual schemes encompassing chemical, biological and physical agents. The current approach is to: (1) accumulate existing data for chemical, biological and physical agents on cell survival, mutagenesis and carcinogenesis that is suitable for dose-response analysis; (2) selection of models that can be applied to the data base in (1); (3) propose conceptual schemes within which further data can be accumulated to answer critical questions raised in (1) and (2).